1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing a display and, more particularly, to a method and apparatus for manufacturing a display whose manufacturing process includes forming a patterned layer on an insulating substrate by vapor deposition in vacuum using a mask.
2. Description of the Related Art
In the manufacture of a flat panel display, a patterned layer is sometimes formed on an insulating substrate by vapor deposition in vacuum using a mask. For example, in the manufacture of an organic electroluminescent (EL) display, an organic layer of an organic EL element is sometimes formed by vacuum evaporation using a mask having an aperture corresponding to each organic EL element.
The existence of water significantly shortens the lifetime of the organic EL element. In the manufacture of an organic EL display, therefore, an insulating substrate is normally heated in vacuum for the purpose of drying before an organic layer is formed. Subsequently, an organic layer is formed without breaking the vacuum.
In this method, drying and film formation are successively performed in vacuum. This makes it difficult to well cool the insulating substrate before the formation of the organic layer is started. As a consequence, the organic layer is formed on the thermally expanded insulating substrate.
Also, in a film formation method such as vacuum evaporation or sputtering, it is originally unnecessary to heat a substrate on which a layer is to be formed. In practice, however, even if the substrate temperature is about room temperature before film formation, it sometimes reaches, e.g., 70° C. or more immediately after film formation.
An organic layer of an organic EL element may contain a hole transporting layer and electron transporting layer in addition to a light-emitting layer. Also, when an organic EL display is designed to be able to display color images, light-emitting layers which emit blue light, green light, and red light are formed in some cases. Therefore, to form an organic layer, it is sometimes necessary to sequentially form a hole transporting layer, blue-emitting layer, green-emitting layer, red-emitting layer, and electron transporting layer.
As described above, the substrate temperature rises by film formation. When film formation for forming an organic layer is performed a plurality of number of times, therefore, not only the substrate temperature rises during film formation, but also the substrate temperature raised by certain film formation has influence on the substrate temperature of film formation performed after that.
As described above, the substrate temperature when a certain layer is formed is affected by heat produced by the formation of that layer and by the substrate temperature at the time the formation of the layer is started. Accordingly, especially when a multilayered structure is used as an organic layer or a plurality of types of light-emitting layers different in emission color are to be formed, the substrate temperature during film formation is difficult to accurately control.
The temperature of an insulating substrate has influence on its dimensions. Therefore, if the substrate temperature during film formation cannot be accurately controlled, each layer cannot be formed in a designed position any longer. If the positional accuracy of each constituent element formed on an insulating substrate is low, it is impossible to realize designed performance.